Lighting apparatus and a method of producing light

Abstract

Light is produced, under the control of a processor 107, having characteristics that change over a daily cycle to reinforce the circadian rhythm of an occupant. Power levels supplied to first, second

Description

The present invention relates to a lighting apparatus for producing light having characteristics that change over a daily cycle to reinforce the circadian rhythm of an occupant. The present invention also relates to a method of producing light over a daily cycle to reinforce the circadian rhythm of an occupant. Daylight received on Earth originates from the Sun which emits radiation as a blackbody, such that the spectrum of emitted light has an average value determined by the temperature of the sun’s surface. With a surface temperature of 5800 K, the maximum energy emitted is at a wavelength of four-hundred-and-ninety nano metres (490 nm) which is a green light in the visible range. However, given that this only represents an average, the actual light emitted covers a much wider spectrum and, in space, the Sun would be perceived as being white. On Earth, the Sun is perceived at midday as being yellow due to the scattering of blue light in the atmosphere; also resulting in the sky being perceived as blue. Before the midday period and after the midday period, the sunlight will need to travel through more of the atmosphere to reach the surface of the earth; which in turn results in a greater degree of scattering. As sunset approaches, the sun appears orange and then red. The scattering of blue light occurs higher up in the atmosphere, such that lower down scattering of orange and red light will also occur, resulting in the colour of the sky changing. It is now known that photoreceptors exist in the eye specifically evolved to respond to the presence of blue light to provide an indication as to the time of day. From this, biological systems are provided for regulating an internal clock which approximates the twenty-four-hour daily cycle and has become known as a circadian rhythm. The ability to detect blue light for this purpose is known as melanopic sensitivity; as distinct from conventional vision which may be identified as photopic sensitivity. Many light sources, including incandescent bulbs, emit blackbody radiation; such that, although there is an average colour temperature, the actual colours present will cover a spectrum. However, recently, there has been a trend towards using light-emitting diodes to produce light, primarily because they are more efficient in terms of producing more light and less heat for a given power rating. However, a problem with light-emitting diodes is that they tend to produce light over narrow wavelength bands. From a photopic position, totally credible white light and a wide gamut of colours can be produced by mixing light derived from a red light-emitting diode, a green light emitting diode and a blue light emitting diode. To facilitate the design of such systems, three-channel drivers are commercially available for driving three distinct channels for the red, green and blue components. This allows many colours to be produced which are satisfactory from a photopic perspective. However, the actual wavelengths present do not emulate the wavelengths present within daylight (blackbody radiation originating from the sun). Furthermore, the filtering of light, as described above, does not occur over a daily cycle, therefore artificial light of this type will fail in terms of synchronising the circadian rhythm of an occupant. Furthermore, if the blue light contribution of a known red, green and blue combination of light emitting diodes is increased, to emulate daylight around noon, having a higher blue component, the narrowband nature of the light emitted by a blue diode will tend to distort the perception of colour in the photopic sense. In particular, this will create difficulties in terms of allowing an occupant to distinguish objects which naturally would be perceived as having blue colours but of different hues. The ability of a light source to present the true colours of objects, compared to natural light, may be quantified as the colour rendering index for the light source. Thus, the colour temperature (the absolute temperature of a black body) determines the apparent colour whereas the colour rendering index is determined by the spectrum of the light. Thus, a further problem exists in that by adapting a system to increase its melanopic sensitivity, a degradation will often occur to the occupant’s photopic sensitivity; which may in turn result in the rejection of the system for providing an appropriate solution to circadian rhythm reinforcement. According to a first aspect of the invention, there is provided a lighting apparatus for producing light having characteristics that change over a daily cycle to reinforce the circadian rhythm of an occupant, comprising: a first driver configured to supply power to a first group of blue light emitting diodes; a second driver configured to supply power to a second group of green light emitting diodes; a third driver configured to supply power to a third group of red light emitting diodes; and a controller configured to independently adjust the level of power supplied by said first driver, said second driver and said third driver over a daily cycle, wherein: said controller is configured to adjust the relative power of said first driver, such that the relative intensity of blue light changes during a daily cycle, to reinforce the circadian rhythm of the occupant; said first group of blue light emitting diodes comprise a first set of blue light emitting diodes for emitting blue light over a first range of wavelengths; said first group of blue light emitting diodes includes a second set of blue light emitting diodes for emitting blue light over a second range of wavelengths, wherein said second range of wavelengths is on average lower than said first range of wavelengths; and said first group of blue light emitting diodes includes a third set of light emitting diodes for emitting blue light over a third range of wavelengths, wherein said third range of wavelengths is on average lower than said second range of wavelengths, thereby maintaining the colour integrity of the blue light as perceived by the occupant throughout the daily cycle. In an embodiment, the first set of blue light emitting diodes emit cyan light at wavelengths below five-hundred-and fifty nano metres (550 nm). The second set of blue light emitting diodes may emit blue light at wavelengths below five-hundred-and-ten nano metres (510 nm). The third set of blue light emitting diodes may emit royal blue light at wavelengths below four-hundred-and-eighty nano metres (480 nm). In an embodiment, the second group of green light emitting diodes emit lime green light at wavelengths below six-hundred-and-eighty nano metres (680 nm). The third group of red light emitting diodes emit red-orange light at wavelengths below seven-hundred-and-thirty nano metres (630 nm). In an embodiment, each group of light emitting diodes comprises two strings of serially connected light emitting diodes connected in parallel. Each string may comprise the same number of light emitting devices and each string may include more than four light emitting devices. In this embodiment, all light emitting diodes in the second group are substantially similar and all light emitting diodes in the third group are substantially similar. In an embodiment, the light emitting diodes for each group are located circumferentially around a support ring. In an embodiment, the apparatus includes a motion detector, wherein the processor is configured to adjust the temporal position of scheduled lighting changes in response to motion detected by the motion detector at times that are inconsistent with an optimal circadian rhythm for an occupant. According to a second aspect of the present invention, there is provided a method of producing light, under the control of a processor, having characteristics that change over a daily cycle to reinforce the circadian rhythm of an occupant, comprising the steps of: adjusting the level of power supplied to a first driver, a second driver and a third driver, wherein said drivers are configured to supply power to respective groups of blue, green and red light emitting diodes; changing the relative power of said first driver, such that the relative intensity of the blue light changes during a daily cycle to reinforce the circadian rhythm of the occupant, wherein: said first group of blue light emitting diodes comprise a first set of blue light emitting diodes for emitting blue light over a first range of wavelengths; said first group of blue light emitting diodes includes a second set of blue light emitting diodes for emitting blue light over a second range of wavelengths, wherein said second range of wavelengths is on average lower than said first range of wavelengths; and said first group of blue light emitting diodes includes a third set of light emitting diodes for emitting blue light over a third range of wavelengths, wherein said third range of wavelengths is on average lower than said second range of wavelengths, thereby maintaining the colour integrity of the blue light as perceived by the occupant throughout the daily cycle. The invention will now be described with reference to the accompanying Figures, of which: Figure 1 shows a schematic representation of a lighting apparatus; Figure 2 shows a schematic representation of a first driver identified in Figure 1; Figure 3 shows a first group of blue light-emitting diodes; Figure 4 shows the construction of a lighting apparatus according to the present invention; Figure 5 illustrates a lighting ring of the apparatus shown in Figure 4; Figure 6 shows the further assembly of the lighting apparatus identified in Figure 4 including the addition of a glass diffuser; Figure 7 shows the connection of the apparatus of Figure 4 to an electricity supply; Figure 8 shows a visible frequency spectrum; Figure 9 shows the spectrum of Figure 8 with reference to the deployment of light-emitting diodes; Figure 10 shows an enlarged portion of the spectrum identified in Figure 9; Figure 11 illustrates lighting adjustments made over a twenty-four-hour cycle to enhance the circadian rhythm of an occupant; Figure 12 illustrate a resulting lighting cycle; Figure 13 illustrates motion detection; Figure 14 details procedures identified by the microcontroller identified in Figure 1; Figure 15 illustrates procedures for monitoring sensors; Figure 16 details further procedures performed by the microcontroller; Figure 17 illustrates lighting adjustments in response to detected motion; and Figure 18 shows alternative adjustments in response to the detection of motion. Figure 1. A schematic representation of a lighting apparatus for producing light having characteristics that change over a daily cycle to reinforce the circadian rhythm of an occupant is shown in Figure 1. The apparatus has a first driver 101 configured to supply power to a first group 102 of blue light-emitting diodes. In addition, the apparatus has a second driver 103 configured to supply power to a second group 104 of green light-emitting diodes. In addition, the apparatus includes a third driver 105 configured to supply power to a third group 106 of red light-emitting diodes. A microcontroller 107 is configured to independently adjust the level of power supplied by each of the drivers 101, 103, 104 to their respective groups 102, 104, 106 of light-emitting diodes over a daily cycle, in response to instructions received from read-only memory 108. In an embodiment, the read-only memory 108 may be implemented as electrically erasable read-only memory to facilitate firmware upgrades. The microcontroller 107 adjusts two attributes of light emitted by the apparatus over a twenty-four-hour daily cycle. The overall amplitude of the light is adjusted such as to provide light when it is required and remove the light when it is not required. The light is provided substantially over normal daylight periods and its intensity may be increased, possibly to a maximum, substantially around midday. In addition to adjusting the overall amplitude of the light, the controller is also configured to adjust the colour of the light. In particular, the relative quantity of blue light is increased around midday relative to the intensity of blue light during the early morning and late evening portions of the day. In an embodiment, no blue light is emitted at these times. The embodiment of Figure 1 also includes a motion detector 109. In an embodiment, the motion detector 109 is configured to identify occupant movement. Furthermore, if movements are detected during periods when it would be expected for the occupant to be asleep, this may be interpreted as a disruption to the occupant’s circadian rhythm. Consequently, adjustments may be made to the positions in time at which transitions occur in an attempt to bring the occupant’s circadian rhythm back into synchronism with a normal operational day. Thus, in the embodiment of Figure 1, the microcontroller 107 is configured to adjust the relative power of the first driver 101, such that the relative intensity of blue light changes during a daily cycle, to reinforce the circadian rhythm of an occupant. In this embodiment, non-midday light is produced by an appropriate green light-emitting diode and an appropriate red light-emitting diode. To achieve the required intensity of light, multiple similar light-emitting diodes are included within the apparatus. At midday, cyan light is required at around five-hundred nano metres (500 nm) and light-emitting diodes are available that can produce light centred around this wavelength. However, known devices produce a relatively narrow band of cyan light such that, when attempting to produce white light, a somewhat unnatural colour results, with a relatively low colour rendering index. Such a problem is difficult to overcome, given that physical constraints exist in terms of the size of the lighting apparatus and economic constraints also exist in terms of the total cost of constructing the apparatus. The present invention is intended for a substantially domestic environment and aims to support the circadian rhythm of a (possibly elderly) occupant. The lighting apparatus cannot be too expensive, while at the same time it cannot produce light that is clearly perceived as being artificial. In the embodiment of Figure 1, each group 102, 104, 106 comprises a plurality of light-emitting diodes. Experiments have shown that each colour of LED has a different forward voltage, such that the total voltage drop of the combination will vary significantly between groups; therefore, for a constant supply voltage, the voltage required to be dropped across the respective driver will vary for the different channels. Consequently, as shown in Figure 1, three individual driver circuits are provided, as described further with reference to Figure 4. The provision of three separate devices also facilitates the optimisation of current flow through the light emitting devices so as to make them brighter. For the third group 106 a single LED type is available that covers a wide orange and red spectrum. Similarly, there is also a single lime green LED that can be used for the second group 104 so, in combination, these do improve the colour rendering index. However, commercially available blue light emitting diodes produce a relatively narrow band of blue light. This would result in the presentation of an unacceptable colour rendering index and therefore the integrity of the light would be considered unacceptable. In the embodiment shown in Figure 1, in accordance with the invention, similar light-emitting diodes are used for the second (green) group 104 and similar light-emitting diodes are used for the third (red) group 106. However, the first group 102 of blue light emitting diodes comprise: a first set of blue light emitting diodes for emitting blue light over a first range of wavelengths; a second set of blue light emitting diodes for emitting blue light over a second range of wavelengths, wherein the second range of wavelengths is on average lower than said first range of wavelengths; and a third set of light emitting diodes for emitting blue light over a third range of wavelengths, wherein the third range of wavelengths is on average lower than said second range of wavelengths, thereby maintaining the colour integrity of the blue light as perceived by an occupant throughout the daily cycle. Figure 2 Light-emitting diodes are operated in a constant current mode therefore the amplitude of current flowing through the devices is not varied to adjust brightness, as would be the case with a standard ohmic incandescent lamp. To maintain constant current operation, the devices are either fully on or fully off and switching operations are performed at a relatively high frequency under the procedure known in the art as pulse-width modulation. Reliable current flow is maintained by the presence of an inductor 201 of a size determined by the overall current flow characteristics; in this embodiment, the inductor 201 has an inductance of sixty-eight milli henrys (68mH) and is capable of conveying up to one-point-seven-five amps (1.75 A). Voltage from a voltage source 202 is regulated by a Zenner diode 203. A schematic representation of the first driver 101 is shown in Figure 2 and may be based around an integrated circuit supplied by Diodes Inc under the commercial designation AL8862. A control input 205 receives pulse-width modulated signals from the microcontroller 107. For any particular level of required output, an appropriate mark-space ratio for the pulse modulated signal is read from a lookup table contained within the read-only memory 108. In this embodiment, each channel can be configured to have a maximum constant current of four-hundred milli amps (400mA). In this embodiment, a supply voltage 202 of twenty-four volts (24V) is provided. The voltage drop across the first group of blue light-emitting diodes is therefore less than twenty-four volts to provide headroom for the integrated circuit 204. The integrated circuit 204 is configured for its respective channel to ensure that there is sufficient voltage to energise the channel’s light-emitting diodes and sufficient voltage to energise the integrated circuit; while at the same time not requiring too much of the power to be dissipated by the integrated circuit 204, which could result in failure. The integrated circuit 204 may provide a maximum constant current of one-point-five amps (1.5A), however, a feed-back resistor 206 limits this current. In this example, resistor 206 has a resistance of zero-point-two-five ohms (0.25 ohm) and as such allows four-hundred milli-amps (400 mA) to flow. Noise filtering on the input side is provided by input capacitors 207. An output capacitor 208 of one-hundred nano farads (1 OOnF) provides further filtering on the output stage. Figure 3 The first group 102 of blue light-emitting diodes (LEDs) is illustrated in Figure 3. In this embodiment, each group consists of two serial strings of seven devices connected in parallel. For the second group 104 of green LEDs, all of the devices are substantially similar and produce lime coloured light. Similarly, in this embodiment, the third group 106 of red LEDs are also substantially similar and produce orange / red light. However, for the first group 102 of blue LEDs there is a first-set 301 of six royal blue LEDs, a second set 302 of two phosphor coated blue LEDs and a third set 303 of six cyan LEDs. Thus, the first group 102 of blue light-emitting diodes comprises a first set 301 of blue light-emitting diodes for emitting blue (cyan) light over a first range of wavelengths. In addition, the first group 102 of blue light emitting diodes includes a second set 302 of blue light emitting diodes for emitting blue light (PC blue) over a second range of wavelengths, wherein the second range of wavelengths is on average lower than the first range of wavelengths. In addition, the first group 102 of blue light-emitting diodes includes a third set 303 of light-emitting diodes for emitting blue light over a third range of wavelengths (royal blue) wherein the third range of wavelengths is on average lower than the second range of wavelengths, thereby maintaining the colour integrity of the blue light as perceived by an occupant throughout the daily cycle. In the embodiment shown in Figure 3, each group of light-emitting diodes comprises two strings of serially connected light-emitting diodes connected in parallel. In the embodiment, a total of seven light-emitting diodes are connected in series to create a string. However, it should be appreciated that many configurations are possible to achieve a preferred light output and an optimised electrical performance. In an embodiment, each string has the same number of light-emitting devices and each string includes more than four light-emitting devices. In this embodiment, all light-emitting diodes in the second group are substantially similar and all light-emitting diodes in the third group are also substantially similar. Figure 4 As shown in Figure 4, the lighting apparatus is constructed upon a housing 401. The housing 401 supports a main circuit board 402 upon which are mounted the integrated circuit 204 along with a second similar integrated circuit 405 (for the green channel) and a third similar integrated circuit 406 for the red channel. Figure 4 also shows the reverse side of a lighting ring 407 upon which the light-emitting diodes are mounted. Figure 5 The lighting apparatus of Figure 4 is also shown in Figure 5, after the main circuit board 402 has been located within the housing 401. A first lightemitting diode 501 along with a second light-emitting diode 502 etc are shown mounted on the front surface of the lighting ring 407. In addition, a housing cover 511 has been located around the housing 401. Figure 6 As shown in Figure 6, assembly of the lighting apparatus is completed by the addition of a glass diffuser 601. The glass diffuser may be attached by being threaded upon the housing 401 and it may abut against the housing cover 511. Figure 7 An assembled lighting apparatus 701 is shown in Figure 7. The lighting apparatus includes a standard connector 702 which, in the example shown in Figure 7, is of the bayonet type although, in alternative embodiments, it may be presented as an Edison screw. This locates within a standard socket 703 and if preferred, the lighting apparatus may be surrounded by a shade 704. After deployment, the light is switched on, possibly using a conventional wall mounted switch. Thereafter, it is not necessary nor desirable to activate this switch again; given that the level of light output, along with its colour spectrum, will be adjusted over a twenty-four-hour cycle. In an embodiment, to synchronise the apparatus with the natural twenty-four-hour cycle, the light switch may be activated at a particular time of day, say twelve noon, such that an initiation process performed on the microcontroller 107 will establish a time of twelve noon for an internal clock. Figure 8 A visible frequency spectrum is illustrated in Figure 8. The spectrum ranges from three-hundred and eighty nano metres (380 nm -violet and almost ultraviolet) to seven-hundred-and-fifty nanometres (750 nm - red and almost bordering on infrared). A true blackbody, at the appropriate temperature, will radiate across this visible spectrum, thereby presenting a high colour rendering index. For the present application, it is necessary to adjust the perceived colour and, in particular, to change the relative intensity of blue light during waking hours. Thus, blue light is required around noon but should not be present at other times; thereby facilitating circadian rhythm synchronisation. To achieve this, the visible spectrum may be divided into a blue region 801, a green region 802 and a red region 803. To maintain the high colour rendering index, all wavelengths allocated to a particular region should be present within that region (as illustrated in Figure 8) and with a distribution of this type, the individual regions have been referred to as “top hats”. In the example shown in Figure 8, a first small gap 811 exists in the transition between blue and green, and a second small gap 812 exists in the transition between green and red. However, even with these gaps present, the colour rendering index is still high; above ninety-five. Thus, the distribution of Figure 8 may be considered an ideal distribution in situations where it is necessary to divide the full visible spectrum into three separate regions of blue, green and red; and primarily when dividing the spectrum between blue and lower frequency colours. Figure 9 The visible spectrum described with reference to Figure 8 is shown in Figure 9. In Figure 8, ideal blue light is illustrated at 801, ideal green light at 802 and ideal red light at 803. Light-emitting diodes capable of achieving these idealised spectra are not commercially available. In an embodiment, the best fit light-emitting diodes are selected in an attempt to achieve a spectrum that is as close as possible to that described with reference to Figure 8, while keeping the design within realistic commercial constraints. In an embodiment, the red light emitting diodes 106 are implemented as diodes capable of emitting red-orange light at wavelengths below seven-hundred-and thirty nano metres (730nm), achieving a red spectrum 901. In practice, red light is emitted from seven-hundred-and-twenty-five nano metres (725nm) down to five-hundred-and-seventy-five nano metres (575nm) as illustrated by a first range bar 902. Thus, this light-emitting diode provides a substantially wideband spectrum for the red channel 803. In an embodiment, the green channel 802 is implemented using lime green light-emitting diodes emitting light at wavelengths below six-hundred-and-eighty nano metres (680nm), achieving a green spectrum 903. In practice, these light-emitting diodes emit light from six-hundred-and-seventy-five nano metres (675nm) down to five-hundred nano metres (500nm) as illustrated by a second range bar 904. To complete the full spectrum and to provide an acceptable colour rendering index, it would be desirable to provide blue light down to at least four-hundred-and-twenty-five nano metres (425nm) as indicated by a third range bar 905. To achieve the required circadian stimulus, it is necessary to produce blue light over a range centred around five-hundred nano metres (500nm) which is usually perceived as cyan. Light-emitting diodes emitting cyan light are available and produce a cyan spectrum 906. The cyan spectrum 906 does satisfy the requirement for circadian stimulation and ranges from five-hundred-and-forty nano metres (540nm) down to four-hundred-and-seventy-five nano metres (475 nm). However, as illustrated in Figure 9, to maintain a high-quality colour rendering index, the spectrum should go down to four-hundred-and-twenty-five nano metres (425nm). In the example shown in Figure 9, a colour gap 907 exists between four-hundred-and-seventy-five nano metres (475nm) and four-hundred-and-twenty-five nano metres (425nm). This significantly undermines the integrity of the emitted light by drastically reducing the colour rendering index of the emitted light to an extent that white light generated by this combination will successfully stimulate the circadian rhythm but will also appear unnatural and even irritable to some occupants. Figure 10 The apparatus described with reference to Figure 1 to Figure 7 facilitates the deployment of a method of producing light under the control of a processor 107, having characteristics that change over a daily cycle to reinforce the circadian rhythm of an occupant. The method adjusts the level of power supplied to a first driver 101, a second driver 103 and a third driver 105. The drivers are configured to supply power to respective groups of blue (102), green (104) and red (106) light-emitting diodes. The method further comprises changing the relative power of the first driver, such that the relative intensity of the blue light changes during a daily cycle to reinforce the circadian rhythm of an occupant. As described with reference to Figure 9, the provision of a single light emitting diode type for generating blue light results in the creation of a colour gap 907; such that the resulting combination of emissions produces light with a low colour rendering index. The present invention overcomes this problem by providing a first set 301 of blue light-emitting diodes for emitting a blue light over a first range of wavelengths 1001. The first group further includes a second set 302 of blue light-emitting diodes for emitting blue light over a second range of wavelengths 1002, wherein the second range of wavelengths 1002 is on average lower than the first range of wavelengths 1001. Furthermore, the first group 102 of blue light-emitting diodes includes a third set 303 of light-emitting diodes for emitting blue light over a third range of wavelengths 1003, wherein the third range of wavelengths 1003 is on average lower than the second range of wavelengths, thereby maintaining the colour integrity of the blue light as perceived by an occupant throughout the daily cycle. In an embodiment, as illustrated in Figure 10, a first blue (cyan) spectrum 1001 is emitted at wavelengths below five-hundred-and-fifty nano metres (550nm) from the first set 301 of blue light-emitting diodes. In the embodiment of Figure 10, cyan light is emitted from five-hundred-and-fifty nano metres (550nm) down to four-hundred-and-seventy-five nano metres (475nm), as shown by a fourth range bar 1004. In the embodiment of Figure 10, a second blue light spectrum 1002 is emitted at wavelengths below five-hundred-and-ten nano metres (510nm) by the second set 302 of blue light emitting diodes. These devices are known in the art as PC blue devices; produced by the deployment of a phosphor coating. In the embodiment, they emit light from five-hundred nanometres (500nm) to four-hundred-and-fifty nanometres (450nm) as indicated by a fifth range bar 1005 In the embodiment of Figure 10, the third set of light-emitting diodes 303 emit a second (royal) blue spectrum 1003 at wavelengths below four-hundred-and-eighty nano metres (480nm). In an embodiment, the royal blue lightemitting diodes emit light between four-hundred and seventy-five nano metres (475nm) and four-hundred-and-twenty-five nano metres (425nm), as shown by a sixth range bar 1006. Thus, by the provision of PC blue diodes and royal blue diodes, in addition to the cyan diodes, a wideband channel has been created for the blue portion of the spectrum by combining a mixture of colours. In this embodiment, three colours have been mixed but alternative embodiments may have four or five colours etc in the blue channel. Furthermore, in this embodiment, only a single type of light-emitting diode type has been used for the green portion 802 and only a single type of light-emitting diode has been used for the red portion 803. However, in alternative embodiments, multiple types of light-emitting diodes may be deployed to widen these green and red channels by colour mixing. Figure 11 In an embodiment, the apparatus may include a separate real-time clock and this clock may be synchronised to an external source, such as GPS time. In this way, it is possible for time corrections to be made automatically when changes are made for light saving purposes. In an embodiment, the processor is configured to maintain a real-time count of elapsed time and establish a daily lighting cycle by periodically addressing a look up table. In this embodiment, each day is substantially similar because it is the overall objective to synchronise a biological circadian rhythm by means of a daily lighting cycle. In an embodiment, a daily lighting cycle is established by the microcontroller 1101 which periodically addresses a look up table. An example of a look up table is shown in Figure 11. It is possible for the apparatus to be synchronised by arranging for its initial activation to occur at twelve midday (12:00), whereafter the apparatus remains energised throughout its operation. However, this deactivation and reactivation procedure may be performed when daylight saving changes are made to national clocks or in response to a power cut. This possibility may also reduce any undesirable impacts on occupants due to daylight saving time related clock changes. The look up table shown in Figure 11 has a first column 1101 that is addressed as an indication of time in response to the real-time count maintained by the microcontroller 107. A second column 1102 and a third column 1103 store the returned data. The second column 1102 identifies the light intensity of the second group 104 of green light emitting diodes and the third group 106 of red light emitting diodes. The third column 1103 identifies a light intensity for the first group 102 of blue light emitting diodes. The established daily lighting cycle activates the light source to a first level at a first time; it then increases the light to a maximum level at a second time; the light level is then decreased to a third level at a third time and is deactivated at a fourth time. Consequently, the lighting levels may be identified as falling into one of four blocks representing the morning when the lights are on but to a low level, midday when the intensity of the light is increased, evening when the lighting level is again reduced and night-time when the lighting device is deactivated. Furthermore, during the second block the first group of blue light emitting diodes is also activated, thereby changing the colour of the light during this block to provide circadian stimulation. After activating the apparatus, the microcontroller 401 initiates its count and operates on the assumption that it is now twelve midday (12:00). The time interval therefore falls between 12:00 and 12:29. An interrogation of the look up table of Figure 11 is made which returns results to the effect that the second and third group should be energised to ninety percent and the first group should be energised to seventy-five percent. Similar results are obtained when an interrogation is made between 12:30 and 12:59. However, as shown in Figure 1, when an interrogation is made between 17:00 and 17:29, data is returned back to the effect that the second and third group are to be energised to sixty percent and the first (blue) group is to be turned off. Again, as indicated in Figure 11, if an interrogation is made between 24:00 and 00:29, all three groups are turned off. If an interrogation is made between 8:00 and 8:29, in this example, the status is similar to that identified for 17:00, in that the second and third groups are energised to sixty percent and the first group is not energised. This situation continues until 10:30 at which point second (green) and third (red) groups are energised to ninety percent and the first group (blue) is energised to seventy-five percent. In this embodiment, changes occur at a granularity of thirty minutes but in alternative embodiments these blocks could be larger or smaller. Thus, in an embodiment, the look up table could include specific data for each ten-minute interval. Furthermore, more changes could occur throughout the day such that transitions from low light levels to high light levels could be more gradual. Figure 12 The apparatus is configured to output light that affects the circadian rhythm of an occupant. Furthermore, data can be taken from the environment and uploaded for long term analysis. This could, for example, result in the look up table described with reference to Figure 11, being updated to compensate for long-term trends. However, an embodiment provides a stand-alone solution, in that information taken from the environment is processed and manipulated within a feedback scenario such that, locally, changes may be made to the daily lighting cycle. It is known that for occupants suffering from mental degradation, including dementia, their situation in relation to sundowning can be improved by the provision of a lighting stimulus. Thus, the inclusion of these automated systems may facilitate independent living by improving mood and reducing the risk of occupants experiencing falls and other accidents. An example of a lighting cycle is shown in Figure 12. The cycle runs from midday to midday and consists of four identifiable blocks of lighting requirements. A first block 1201 represents the evening and during this interval the first group 102 is off and the power supplied to the second group and the third group is at sixty percent, as shown at 1211. A second block 1202 represents the night time when no light is required, as indicated at 1212. At 21:00 a transition between the first block 1201 and the second block 1202 occurs and this has been identified as a preferred time for the occupant to start sleeping. A third block 1203 represents the early morning where again, as indicated at 1213, the second and third groups are energised to sixty percent and the first group is switched off. The fourth block 1204 represents the middle of the day and the intensity of the light is increased during this interval. Thus, as indicated at 1214, the second group and the third group are energised to ninety percent. Furthermore, as indicated at 1215, the first group is also energised to a predetermined level which, in this embodiment, is seventy-five percent. In terms of synchronising the circadian rhythm of the occupant, greater stimulation may be provided by increasing the lighting level during the fourth interval 1204 and, in particular, increasing the lighting level of the first (blue) group. Alternatively, or in addition, the duration of interval 1204 may be increased by occurring sooner, achieved by extending block 1204 in the direction of a first arrow 1221 and / or by increasing fourth block 1204 in the direction of a second arrow 1222. An embodiment takes account of adjustments that may be made to enhance (midday) circadian stimulation, as described above. However, an embodiment is concerned with the second interval 1202 which relates to an occupant’s sleeping patterns. The system of this embodiment has been preprogrammed to assume that sleep will start at 21:00, as indicated at 1223 and that sleeping will stop (the occupant will awake) at 07:00, as indicated at 1224 It may be assumed that there is an interval 1225 during which an occupant is asleep. In addition, there is a first window of interest 1231 representing the transition from being awake to being asleep. Similarly, there is a second window of interest 1232 representing the transition from being asleep to being awake. These transitions should occur as indicated at 1223 and 1224 respectively. However, these transitions may drift (advance or retard) with respect to time and an objective of an embodiment is to discourage transition drifting of this type. Figure 13 The first window of interest 1231, along with the second window of interest 1232 are shown in Figure 13. The first window of interest 1231 is based around the time of 21:00 representing the time at which the occupant is expected to fall asleep. The window of interest 1231 is therefore divided into a first evaluation window 1301 and a second evaluation window 1302. Similarly, the second window of interest 1232 is based around the expected time of 07:00 that the occupant is expected to wake and is therefore divided into a third evaluation window 1303 and a fourth evaluation window 1304. During the first evaluation window 1301, the occupant should be awake and therefore activity should be detected. If no activity is detected, this may indicate that the occupant has fallen asleep early; and this may in turn disrupt their circadian rhythm. Similarly, during the second evaluation window 1302, the occupant should be sleeping, therefore activity is not expected. The detection of activity in the second evaluation window 1302 may suggest that the occupant is still awake when they should be sleeping. During a third evaluation window 1303, the occupant should be sleeping therefore a detection is made as to whether activity is present. Similarly, during the fourth evaluation window 1304, the occupant should be awake, therefore activity should be present. Adjustment may be required if no activity is detected during the fourth evaluation window. Figure 14 Procedures implemented by the microcontroller 107, to achieve the activities described with reference to Figure 11 to Figure 13, are shown in Figure 14. At step 1401 the system is activated in response to receiving power. Thus, in an embodiment, the electric lighting apparatus is installed and then switched on at twelve noon (12:00). Thus, upon activation, the internal clock or counter is set to 12:00 at step 1402. In an embodiment, the electric lighting apparatus arrives preconfigured and is ready for deployment straight out of the box. In an alternative embodiment, it is possible for configuration procedures to be performed; possibly by receiving data from a remote database or, alternatively, in response to local input possibly received via a wireless connected tablet. Thus, at step 1403 a lookup table is downloaded, of the type described with reference to Figure 11 and the sleep window is established, as represented by block 1202 described with reference to Figure 12. The system is now operational. At step 1404 the lookup table is read based on the time identified by the clock / counter. At step 1405 the lights are energised in response to the data received from the look up table. Given that the system has just been energised, the time will be shortly after 12:00 resulting in the second and third groups being energised to ninety percent and the first group being energised to seventy-five percent. At step 1406 a question is asked as to whether an adjustment flag has been set and on a first iteration this flag will not have been set. The setting of the flag and the creation of related data is performed in response to activity detections. On subsequent iterations, movement detections will have been made and this may result in some values in the look up table being adjusted at step 1407. At step 1408 the sensors are monitored and the actual nature of these monitoring operations will vary depending upon the time of day. For example, movement detection is not required outside the windows of interest. At step 1409 a question is asked as to whether an alarm condition has been identified and when answered in the affirmative an alarm is raised at step 1410 When the question asked at step 1409 is answered in the negative (the usual case) the look up table will be read again at step 1404 and procedures 1404 to 1409 will be repeated in a substantially continual way during the normal operation of the lighting apparatus. Figure 15 Procedures 1408 for monitoring the motion sensor 109 are detailed in Figure 15. At step 1501 a question is asked as to whether no activity has been detected. This is relevant for the first evaluation window 1301 and the fourth evaluation window 1304. Thus, if the process is not considering the time interval for the first evaluation window 1301 or for the fourth evaluation window 1304, the question asked at step 1501 will be answered in the negative. If the question asked at step 1501 is answered in the affirmative, activity detection is performed at step 1502. If no activity is detected, a flag is set at step 1504. Otherwise, no flag setting is performed. At step 1505 a question is asked as to whether activity is being detected which is relevant for the second evaluation window 1302 and the third evaluation window 1303. Thus, if these intervals are not being considered, the question asked at step 1505 will be answered in the negative. At step 1506 activity detection is performed and a question is asked at step 1507 as to whether activity has been identified. On this occasion, activity should not be occurring therefore if the question asked at step 1507 is answered in the affirmative a flag is set at step 1508. It can be appreciated that assessments will have been made to identify how much activity constitutes an activity worthy of attention. In an embodiment, within each interval, it may be necessary for an activity to be identified on several occasions within the interval. Thus, a threshold may exist to the effect that if an activity is identified less than three times (on three separate iterations) the setting of the activity flag is not triggered. Figure 16 Further procedures performed by the microcontroller 107 are shown in Figure 16. These procedures consider the data collected following the implementation of the monitoring procedures, such that changes may be monitored on a day-to-day basis. When activity is detected in the second evaluation window and the third evaluation window, or the lack of activity is detected in the first evaluation window or in the fourth evaluation window, adjustments are not made in response to detections made on a single day. An assessment is made as to how many days are considered to be allowed before an adjustment is made. In this example, it is necessary for these evaluations to have been identified on three consecutive days and only then is an adjustment made. At step 1601 a question is asked as to whether the first evaluation window 1301 is to be considered. If affirmative, a question is asked at step 1602 as to whether no activity has occurred during the evaluation window. If answered in the affirmative, a question is asked at step 1603 as to whether this lack of activity has occurred over three consecutive days. If answered in the affirmative, the end of the day is extended. At step 105 a question is asked as to whether the second evaluation window is to be considered and if answered in the affirmative, a question is asked at step 1606 as to whether activity has been detected. If answered in the affirmative, a question is asked at step 1607 as to whether this activity has occurred over three consecutive days. If answered in the affirmative, the end of the day is reduced at step 1608. A question is asked at step 1609 as to whether the third evaluation window 1303 is to be considered and when answered in the affirmative, a question is asked at step 1610 as to whether activity has occurred. When answered in the affirmative, a question is asked as to whether this activity has been detected over three consecutive days and when answered in the affirmative the morning is delayed at step 1612. At step 1613 a question is asked as to whether the fourth evaluation window 1304 is to be considered and when answered in the affirmative, a question is asked at step 1614 as to whether no activity has been detected. If answered in the affirmative, a question is asked at step 1615 as to whether this has occurred for three constricted days and when answered in the affirmative, the morning is advanced at step 1616. Figure 17 The first window of interest 1231 is shown in Figure 17 in which, for the occupant, a transition should take place at 21:00 from being awake at 1701 to being asleep at 1702. To reinforce and support the circadian rhythm of the occupant, the lights are switched off at 21:00 and thus transition from an interval 1703 during which the lights are on to an interval 1704 during which the lights are off. The first evaluation window 1301 has been monitored and, for the purposes of this illustration, it is now assumed that no activity has occurred in the first evaluation window 1301 for three or more consecutive days. Under these circumstances, the end of the day is extended by moving the transition from lights on to lights off in the direction of a first arrow 1711. To provide a further example, it is now assumed that activity has occurred in the first evaluation window 1301 but activity has also been detected in the second evaluation window 1302 for three or more consecutive days. Under these circumstances, the end of the day is reduced by moving the transition from lights on to lights off in the direction of a second arrow 1712. Figure 18 The third evaluation window has been monitored during which the occupant should be sleeping as indicated at 1801. The occupant should wake at 07:00 such that during an interval 1802 the occupant is awake. During interval 1801 the lights would normally be off as indicated at 1803, and the lights would be switched on for interval 1802 as indicated at 1804. For the purposes of this example, it is assumed that activity is detected during the third evaluation window 1303 as indicated at 1805. To discourage this behaviour, the night-time lights-off interval is extended by moving the transition in the direction of a third arrow 1806 thereby increasing the lights-off interval as indicated at 1807. In an alternative example, it is assumed that no activity is detected during the fourth evaluation window 1304 as indicated at 1811. To discourage this behaviour, the transition from lights off to lights on is advanced as indicated by a fourth arrow 1812, such that the lights-off interval 1813 is now shorter. In practice, it is necessary to make a practical assessment as to what extent it is possible to advance or retard light changing transitions. In the examples described, the length of any particular movement is thirty minutes but in alternative embodiments, this length may be shorter or longer. Furthermore, a decision is required in terms of how many times a transition of this type may take place. In an embodiment, transitions of this type only take place once and the system is then configured to bring the transitions back into their preferred normal positions if at all possible. Thus, if the procedures described above are successful, the occupant will return to their preferred sleep patterns and the timing adjustments may be cancelled. Again, such a procedure may involve making investigations that cover several consecutive days. In an embodiment, if a first movement is unsuccessful, a further movement may occur such that a movement of one hour has taken place from the preferred position of the transition. Theoretically, such transitions could continue but such a situation is likely to be considered undesirable. Thus, in an alternative embodiment, if the system detects that further transition movement should occur, it may be preferable to raise an alarm condition at step 1410 notifying a clinician to the effect that a greater level of intervention may be required or fundamental adjustments may be required to the lighting cycles.

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